Wiping contact type switching apparatus



June 29,-'.-1965 P. v. sARLuND WIPING CONTACT TYPE SWITCHING APPARATUS 2 Sheets-Sheet 1 Filed Jan. 30, 1962 DDD June 29, 1965 P. v. sARLUND WIPING CONTACT TYPE SWITCHING APPARATUS 2 Sheets-Sheet 2 Filed Jan. 30, 1962 kmw www Q INVENTOR ...Pen 7X ,Saruna A TTORNE Y ymatter that may accumulate on the contacts.

- contact assembly having a flat contact surface.

United States Patent O This-invention relates in general to switching apparatus, and more particularly -to a switching arrangement of the ywiping-contact type in which a movable switch contact Y initially wipes a fixed contact before reaching a resting position on that fixed contact.

Wiping action in a switch is desirable since it tends to 'remove from the switch contacts any foreign' material,

such as dirt or grease, which would otherwise interfere with the establishment of an electrical connection between such contacts. A wiping connection is customarily made by wiping one contact on another contact in one direction.

While prior wiping-contact techniques are usually effective in providing dirt-free, resistance-less, electrical connections, it is desirable to enhance further the immuni-ty of switch contacts against the deleterious effects of foreign This is achieved by the present invention which features a novel bi-directional wiping action wherein a movable contact initially wipes an area of a fixed contact in one direction .and subsequently moves backward .to wipe the area in the opposite direction.

Accordingly, it is an object of the present invention to provide a novel switching apparatus.

It is another object to provide a switching arrangement which effects 'bi-directional wiping action of its contacts.

It is a further object to provide a switching arrangement in which the contacts are maintained free of foreign material.

Switchingapparatus, constructedv in accordance with one aspect of the invention, comprises a first stationary A second Contact assembly includes a support and a lresilient member having one end fixed to said support and having a freeend displaced in a given direction from the one end and presenting a second contact surface. Means are provided for pivotally supporting the second assembly for movement in a direction generally the lsame as the given direction from aiirst position in which the contact surfaces are out of engagement, through a second position in which the contact surfaces are engaged with the angle defined by the `flat contact surface and a line from their point of contact to the one end of the resilient member of less than the critical angle, to a final position. The switching appaf ratus also includes means for arresting the movement of `the free end of the resilient member in the given direction after the second assembly has moved from the second position but before it reaches the final position.

The features of thisinvention whichare believed to be new are set forth with particularity in the appended claims. The invention, together with further objects and advantages thereof, may best be understood, however, by reference to the following description in conjunction with the accompanying drawings, in which identical refer-ence numerals indicate identical elements, and in which FIG- URES 1-4 are various views of a switching apparatus embodying the invention. g

Before turning to a description of FIGURES 1 4, -it should be noted that the switching apparatus to be described is disclosed in copending application Serial No. 169,812, filed concurrently herewith, in the name of George V. Morris. The Morris case illustrates the switching apparatus in the environment of a ysubscriber cornmunication receiver, specifically a subscription television 3,1253 Patented .lune 29, 1965 "ice receiver. The switching apparatus is adjustable and must be adjusted by the subscriber in accordance with a given adjustment before a received intelligence signal may be int'clligibly reproduced. The present disclosure only includes that part of lthe Morris et al. application .necessary to illustrate the subject invention. As shown in the Morris case, the switching apparatus is employed to permutably connect a series of input circuits to a series of output circuits in order to permu-tably apply code signal components to encoding circuitry.

Referring now to FIGURES 1-4, a front plate 239 and a back plate 231 are mounted in parallel, spaced apart relationship with respec-t to each other by means of rigid spacing and interconnecting structure (not shown). A perforated movable strip or tape 2.45, lpreferably made of a polyester material such as Mylar, has its end portions respectively wound around a pair of spools or reels, as fully described in the Morris application. Tape 245 has a series of contact making portions, specifically perforations 247, in a sense randomly positioned on the tape. With the exception of halves 247, tape 2&5 is very similar to 35 mm. camera film. Regularly spaced sprocket holes, occupying the standard sprocket hole pitch of 1%@ inch for 35 mm. film, are also disposed along both edges of tape 245.

Tape 245 also has disposed along one edge thereof, a pre-recorded sound track 244. Preferably, the information pre-recorded on track 24d is simply a continuous Vsine wave. As fully explained in the concurrently iiled Morris case, portions of track 24d are erased by means of an erase head 17 l in order to make an internal record of the programs to which a given subscriber has subscribed.

The charges registered on track 244 facilitates au audit for into the regularly spaced sprocket holes of tape 245, causing rotation of the sprocket as tape 245 is transported or moved. Matrix assembly 250 is rigidly connected to plate 2Enl and is positionedintermediate tape guide 24S and sprocket 249. Tape 245 is to be moved from one to another of a multiplicity of distinct and spaced positions, and in each such position a different 5 x6 matrix or permutation pattern of holes 247 is presented to matrix assembly 25h. It has been found that withthis arrangement, a length of film 245 of approximately 31 feet may contain at least 2,000 different 5 x 6 matrix patterns.

Matrix assembly 25% includes a framework 252, preferably constructed o-f plastic. Screws 251 (see FIGURE l) rigidly mount framework -252 `to b-a-ck plate 23d Viewed from vthe top, framework 252 is essentially a four-sided,

rectangularly shaped open structure composed of the two parallel spa-ced legs 252a, yshown in cr-oss section in FIG- URE 2, and the two parallel spaced'legs 252b, shown in cross section in FIGURE 3. A series of five shafts or pins 255 are journaled in and mounted between portions 252a of framework 252. Rods 255 are mounted in parallel, .spaced relationship with respect to each other and also with respect to portions 252b of framework 2.52.

A Ilaterally movable carriage 257 comprises a foursided, rectangular shaped open structure having rtwo parallel spaced portions or legs 257e, shown in cross section in IFIGURE l2, .and two spaced, parallel legs or portions 257i), shown in 'cross section in FIGURE 3. Carriage 2.57 also has an elongated arm'of rectangular cross section lexten-ding from the righ-t leg 25717 f (as viewed in ElGUR'E 3) in the direction ofjand through an aperture of front plate 230. As will be seen, arm 256 serves as .two parallel, bi-l-ar portions.

metallic support plates 260 whichinterconnect rods 255 and 258. Each of plates 260 is electri-cally conductive and substantially tiat except for two end por-tions which are turne-d or `'bent' at right angles to provide tabs or flanges 260e to `facilitate connections between rods 255 4and 258. Flanges 260a are provi-ded with apertures for receiving shafts `255 and l25S. In this Way, each of plates 260 is pivotably. mounted to an assigned one of .rds255 and also to an assigned one of rods 258.

With this construction, framework 252, carriage 257 .aud plates 261i provide Ia parallelogram arrangement, like a set of parallel rules; no matter Whe-re ycarriage 257 is -positioned it is always parallel to the plane defined by rods 255, and support plates 260 are always parallel to each other. The limit of horizontal travel of carriage .257 is'best seen in FIGURE 3. 1 One extreme position of the carriage is shown in that gure in full-line construction. -Portion 252.` of framework 252 provides a stop for carriage 257. When the carriage is more horizontally to the left in FIGURE 3, -it is stoppe-d by portion 252d of framework 252. This extreme position is shown in broken-line construction in FIGURE 3. A pair of coil springs 263 are connected between carriage 257 and frame- .work 252 to urge carriage 257 to the full-line position shown in FIGURE 3.

A cam member 254 (see FIGURE 3), actuated in a manner described in complete detail in the concurrently tiled Morris application,engages arm 256 and pushes it,

Ythereby moving-carriage 257 to the left against the tension of springs 263 and toward back plate 231. Specifically, cam 254 Imoves in a direction perpendicular to and y11p from the view in FIGURE 3.

,live support plates 260; consequently, there is a total of thirty resilientzmembers 265. Each spring 265 consists of a length of conductive wire having a 180 lben-d at the middle such that the wire doubles back on itself to form As viewed in FIGURES 3 an-d 4, each spring member 265is of generally L-shaped configuration, the long leg ofthe L lying Iagainst a surface 260b.and.being mounted at its end portion 26517 to an assigned one of plates 260. More specifically, the

midpoint of the long lleg of the L of each member 265 is loosely retained in a guide 266 formed out of its associated plate 260 and end 265b is rigidly securedV `by means of a tab 273, also formed out of plate 260, and a solder connection 273:1. The s-hort leg of the L, constituting a spring contact 265a, is a free end which protrudes -above its associated. plate 260; it -consists of the two ends of .the single wire comprising a spring member 265.

Thus, each of plates 260 provides a support :tor an vassociated resilient member i265 which has one end 265b xed to the support (by means of tabs 273 andconneo .tions 27'3a), an intermediate portion normally lying against a surface 2605 `of the support, and a free end 265a displaced in a given direction (to the right as'viewed ,in FIGURES 3 and 4) from the intermediate portion and presenting .a contact surface.

The portion of tape 254 extending through Vmatrix 250 .is .disposed immediately above spring contacts 26511. A

printed circuit panel 267 lies above both tape 245 and spring contacts 265a and contains a series of six parallel spaced, flat, conductive strips 267a printed thereon on the side immediately y'adjacent tape 245. Spring contacts 265e and flat contact. surfaces 267a are so positioned with re- "spectto each other that a series of tive contacts 265e,

Y printed circuit panel Y267, 1and it along with pane1-267 is mounted to framework 252 by means of screws 271.

A series of six input circuits or conductors 51-56 are lrespectively electricallyrconnected, such as lby soldering, to the six parallel conductive strips 267a. A series of live output circuits or conductors 6I-65 are respectively electrically :connected to the live plates 260, also by soldering.

ySince plates 260 are constructed of a conductive-material and since conductive springfcontacts 265e are mechanically an-d electrical-ly connected to plates 260 by means of tabs 273 .and solder -connections 273e, output 'conductors L61-65are electrically connecte-d to the contacts 265e of their associated plates 260.

As mentioned previously, springs 263 ^urge carriage 257- to the full-line position shown in FIGURE 3. In lthat position, contacts 265e are spring biased to bear against Vthe underside of perforated tape 245.' If an .aperture 247 in tape 245 liesimmediately above any one of the thirty spring contactsA 265a, thatY Contact projects through the" aperture to make an Velectrical contact with the -conductive strip 267a lying immediately thereabove. iIn FIGURE -3 it willbe observed that the contact 265e ion the extreme rig-ht has a hole 247 .immediately thereabove and it `extends through that aperture to engage a strip 26711. Thus, the pattern of perforations 247 llying rbelow printed circuit panel 267 determines the instantaneous interconnection pattern between input conductors 51-56 and output conductors 61-65.v

In order to change the permutation pattern, the ltape is moved or transported to a differentand spacedposition,

thereby to present a different pattern of apertures 247 to matrix switch assembly 250. Before tape 247 is moved, however, movable switch contacts 265 are preferably displaced from the tape to avoid possible damage to the tape Yand contacts. This is realized by actuating apparatus for cam 254, controlled by the subscriber and fully described in the concurrently tiled Morris application. Such actuation effects lateral movement of carriage 257 toward back plate 231 (to the leftin FIGURE 3) against the bias of springs 263. As-carriage 257 is so moved, movable switch contacts 265e retract so that all Ypressure of the contacts, and

in fact physical engagement, is removed from the under side of tape 245. This premits movement of rilrn 245 without inter-ference from the free ends 265a of resilient rnem ber 265. j

Movement of the tape -is accomplished by a mechanism also illustrated in theconcurrently filed Morris application. Brieiiy, driving meansare shown in that application for selectively driving either one of the two spools, on which the end portions of tape 245 are wound, in order to move the. tape from one position to another. ineither direction. A single control knob, which is to be rotated by the subscriber,l actuates the driving means to permit the subscriber to change the permutation pattern. between input conductor 51-56 and output'conductors 61-65.` Preferably, the

.manual control knob is tobeadjusted differently for each erating shaft 302 controls a cyclometer register (noty shown) and is provided with a mitre gear 353 which meshes with gear 299. Thus, rotation of gear 299, which results from movement of perforated tape 245 in either direction, drives companion gear 303 in order to actuate the cyclometer register. As the cyclometer register is actuated, as is fully explained in the Morris case, different indicia is displayed to the subscriber for each permutation pattern of perforations presented to the input and output switch contacts. In setting up'the switching apparatus for a given program, the subscriber must rotate the control knob until a prescribed indicia is displayed by the register.

ITurning now to the-invention to which the present application is directed, it is to be noted that stationary switch contacts 267e lie above movable contacts 26511. This expedient is employed in order to prevent contamination or fouling of the switching apparatus by settling dust particles. In accordance with the present invention, the contact making arrangement features a unique bi-directional wiping action to insure further that any foreign materials, such as dirt or grease, that may accumulate .on flat contact surfaces 26711, or on contacts 26511, are

displaced so that nothing interferes with the establishment of the elecrtical connections.

The invention is best illustrated by the four separate views A-D making up FIGURE 4. Each of the four views shows a single one of elongated, movable resilient members 265 and its associated plate 260 in four different positions. View A shows the retracted position of resilient member 265 when the contact surface of its free end 26511 is completely out of engagement with tape 245 and the flat contact surface 26711 assigned thereto. The contact surfaces may be so disengaged by moving carriage 257 to the left in FIGURE 3 under the control effect of cam 254. When the cam is subsequently actuated as described in the concurrently filed Morris case (in a perpendicular direction toward the drawingas viewed in FIGURE 3), coil springs 263 cause carriage 257 to move toward front plate 230.

The position in which resilient member 265 finds itself at the instant the contact surface of its free end 265e makes initial contact with its associated stationary fiat contact surface 26711 through a perforation 247 is shown by View B in FIGURE 4. At that instant, there is a force along line 253, which extend-s from the anchor end 265i) of resilient member 265 to the point of contact of free end 26561 and flat contact member 267g, toward surface 26711. In the position shown in View B, the angle defined by dat contact surface 267a and `line 253 is within the critical angle. To elucidate, the force along line 253 and toward fixed contact 2670 may be resolved into two componentsone which is perpendicular to and toward flat contact 26711 and another which is parallel to contact surface 26711 and extending to the right. The critical angle may be defined as that angle in which the perpendicular force component multiplied by the coefficient of friction of flat contact surface 26711 equals the parallel force component. Under such circumstances, resilient spring member 265 would be held in position. However, by making the angle between line 253 and surface 267e less than the critical angle, as in the present invention, the parallel force component is greater than the perpendicular component multiplied by the coefficient of friction, resulting in movement of free end 26511 to the right. Thus, as carriage 257 continues to move to the right in FGURE 3 under the influence of springs 263, shaft 25S moves from the position shown in View B to that shown in View C of FIGURE 4, and during that kmovement free ends 26511 slides or wipes to the right as shown by arrow 259.

To more fully understand the reason that free end 26511 moves to the right as shaft 258 moves in the same direction, it is helpful to consider the effect of the stiffness of resilient member 265. Because of that stiffness the triangle formed by member 265 and lines 253 tends to remain unchanged. In other words, the angle between the short leg 26561 o-f the L and the long leg of the L tends to remain constant. AS

V265e and shorten the line 253 of the triangle. However,

due to the stiffness of member 265, line 253 will tend to remain of the same length in going from the position of Viewv B to that of View C and the only way for this to be accomplished is for resilient member 265 to bend or flex away from surface 26% to the right until it bears against shaft 255. Of course, the greatest bending moment vwill exist at end 265b of spring member 265. Thus, maximum bending takes places at that point.

yin the position shown in View C, flexing of resilient member 265 is arrested by shaft 255. Thus, as support plate 26th and pin 255 continue to pivot to the right about shaft 255, free end 26511 winds around shaft 255 and thus reverses direction and moves to the left as shown by arrow 262. In other words, shaft 255 serves as a fulcrum point for resilient spring member 265 once the position of View C is attained so that as plate 260 approaches the position shown by View D free end 26511 wipes flat contact surface 26711 in the reverse direction.

'By limiting the travel distance of plate 26) from View C to View D, the Contact surface of free end 26511 may be arranged to wipe, in the direction of arrow 262, only part of the area of xed contact 26761 previously .wiped in the direction of arrow 259. Obviously, lsuch bi-directional wiping action is ideal for establishing 4an electrical contact. The movable contact first moves over a prescribed area with a wiping .action to displace foreign materials that may interfere with proper contact and then moves Ibackward on the wiped surface, reaching a final res-ting position within the area wiped clean by the first motion. With `such an arrangement, the possibility of ya faulty electrical connection is virtually eliminated. I

By way of summary, the switching apparatus of the present invention comprises a first stationary con-tact assembly 267, 267a having a fiat contact surface 26711. There is a se-cond contact assembly 266, 255 which includes a support 260 and a resilient member 265 having one end 265b fixed to the `support and having a free end 26561 displaced in a given dir-ection (to the right as viewed in FGURE 4) from the one end 265b and presenting a second contact surface. Shaft 255 and framework 252, in which the shaft is journaled, may be considered means vfor pivotally supporting assembly 260, 265 for movement in a direction generally the same as the given direction from a first position (View A) in which the contact surfaces are out of engagement, through a second position (View B) in which the contact surfaces are engaged, with the angle defined by fiat contact surface 267e and line 253 from their point of contact to end 265b of resilient member 265 of less than the critical angle, to a third position (View C) with a consequent wiping of the second contact surface on fiat contact surface 267:1 in the given direction (as shown by arrow 259), and thence to a fourth and final position as shown by View D. Shaft 255 constitutes means for arresting the movement of free end 26511 of resilient member ,265 in the given direction after the second assembly 266, 265 has moved from the second position (View B) but before it reaches the final position (View D). More specifically, arresting means 255 is effective when the second -assembly reaches the third position (View C), free end 26511 winding around shaft 255 as the Vsecond assembly moves from the third to the fourth positions to effect wiping of the contact surface of free end 26511 on flat contact surface 267c1 in a direction opposite from the given direction, as shown by arrow 262.

Certain features described in the present application are disclosed and claimed in copending application Serial No. 117,431, filed June 15, 1961, in the name of Melvin C. Hendrickson et al., and also in the following copending 7 v applications filed concurrently herewith: Serial Nos. 169,766, in the Vname of George V. M-orris et al., and which issued May 19, 1964, as Patent 3,133,986; and 169,792, in the name of Emil C. Walker, now abandoned, allof which'are assigned to the present assignee.

While particular embodiments of the invention have been shown and described,`modifications may be made,

land it is intended in the appended claims to cover all such modifications as may fall within the true spirit and scope of the invention.

I claim:

1. Switching apparatus comprising:

` a first stationary contact assembly having a fiat contact surface;

a second contact assembly including a support and an elongated Vresilient member having one end fixed to said support, having an intermediate portion normally lying again-st a surface of saidsupport, and having a free end displaced in a given direction from said intermediate portion and presenting a second contact surface; l

and means including a shaft for pivotally supporting said second assembly for movement about a fulcrum point defined -by said shaft in a direction generally the same as said given direction from a first position in which said contact surfaces are out of engagement, through a second position in which said contact surfaces are engaged to a third position, said intermediate portion of said resilient member flexing away Y from said surface and toward said fulcrum point to effect wiping of said second contact surface on said fiat contact surface in said given direction, and thence to a fourth and final position;

said shaft arresting the flexing of said intermediate portion and the movement of said free end when said ysecond assembly reaches said third position, and said free end winding around said `shaft as said second assembly moves from said third to said fourth position to effect wiping of said second contact` surface on said flat contact surface in a direction opposite Y from said given direction.

2. Switching apparatus comprising:

Y a first resilient switch contact;

a second switch contact;

an actuating member to which said resilient -contact is mounted;

means mounting said actuating member for motion in a predetermined continuous, unidirectional path, said resilient contact wiping a prescribed area of said second contact in a given direction in response to motion of said actuating member along a first portion of said predetermined path;

and means coupled to said actuating member for causing said resilient contact, in response to continued motion of said actuating member along a second and subsequent portion of said path, to wipeat least a portion of said prescribed area in the reverse direction and to revert to a rest position in electrical contact with said second contact within said prescribed area.

'3. Switching apparatus comprising: Y

a stationary switch contact having a fixed conta-ct surface;

a movable resilient switch contact presenting a movable contact surface;

an actuating member to which said movable switch contact is mounted;

means mounting said actuating member for motion in a predetermined continuous, through a sequence of first, `second third andffourth consecutive positions;

means coupled to said actuating member for holding unidirectional p a t h.

K said contact-surfaces out of engagement during the movement of said actuating member from its first to its second positions, said movable contact surface prewiping a prescribed area of said fixed contact surface in a given direction during the movement of said actuating member fromfits second to i-ts third l positions;

and means coupled t-o said actuating member for causing `said movable contact surface to wipe at least a portion of said prescribed area in the reverse direction during the movement of said actuating member from its third to its fourth positions, said movable contact surface thereby coming to rest within the areay initially prewiped.

d. Switching apparatus comprising:V

a stationary contact assembly having a fixed contact surface;

fa movable contact assembly including a resilient spring memberpresenting a movable contact surface;

meansfor mounting said movable Contact assembly for Y unidirectional movement from a first position in which said -contact surfaces are out of engagement, through :second and third positions wherein said mov- `able contact surface engages and wipes a prescribed area of said fixed contact surface in a given direction, Vand thence to a fourth and resting position;

and means operableduring the movement of said movable contactassembly from said third to said fourth positions for effecting wiping of said movable contact surface lon a portion of said prescribed area of said xed contact surface in a direction opposite from said given direction, said movablel contact surface thereby coming to rest within said prescribed area.

5. Switching apparatus comprising:

a stationary contact assembly having a flat, fixed contact surface; l

.a movable contact assembly including a support and an elongated resilient spring member having one end secured to said support in cantilever fashion and having `a free end angularly displaced from said secured end and Ipresenting a movable contact surface;

means for pivotally mounting -said movable contact assembly for movement of said secured end of said spring member about a fulcrurn pointin a given direction along a path which is generally parallel to said flat contact surface from a rst position in which said conta-ct surfaces are out of engagementythrough second and third posi-tions'wherein said movable contact -surface engages and exerts a force toward Isaid flat Contact surface, the force having a component parallel to said fiat contact surface in said given Adirection and of a magnitude to effect flexing of said spring member with a consequent wiping of said movable contact surface on a prescribed area of said flat contact surface in said given direction; and thence to a fourth and resting position;

and means for arresting the flexing of said spring memberwhen said secured end reaches said third position and for winding said free end .of said spring member about said fulcrum p-oint as said secured end moves from said third to said fourth positionsto effect wiping of said movable contact surface on atleast a portion of said prescribed area of said flat contact surface lin a direction opposite from said given direction.

References Cited by the Examiner UNITED STATES PATENTS 1,864,369 6/32 Pepper V ZOO-164 X i BERNARD A. GILHEANY, Primary Examiner.

'ROBERT K. SCHAEFER, Examiner. 

1. SWITCHING APPARATUS COMPRISING: A FIRST STATIONARY CONTACT ASSEMBLY HAVING A FLAT CONTACT SURFACE; A SECOND CONTACT ASSEMBLY INCLUDING A SUPPORT AND AN ELONGATED RESILIENT MEMBER HAVING ONE END FIXED TO SAID SUPPORT, HAVING AN INTERMEDIATE PORTION NORMALLY LYING AGAINST A SURFACE OF SAID SUPPORT, AND HAVING A FREE END DISPLACED IN A GIVEN DIRECTION FROM SAID INTERMEDIATE PORTION AND PRESENTING A SECOND CONTACT SURFACE; AND MEANS INCLUDING A SHAFT FOR PIVOTALLY SUPPORTING SAID SECOND ASSEMBLY FOR MOVEMENT ABOUT A FULCRUM POINT DEFINED BY SAID SHAFT IN A DIRECTION GENERALLY THE SAME AS SAID GIVEN DIRECTION FROM A FIRST POSITION IN WHICH SAID CONTACT SURFACES ARE OUT OF ENGAGEMENT, THROUGH A SECOND POSITION IN WHICH SAID CONTACT SURFACES ARE ENGAGED TO A THIRD POSITION, SAID INTERMEDIATE PORTION OF SAID RESILIENT MEMBER FIXING AWAY FROM SAID SURFACE AND TOWARD SAID FULCRUM POINT TO EFFECT WIPING OF SAID SECOND CONTACT SURFACE ON SAID FLAT CONTACT SURFACE IN SAID GIVEN DIRECTION, AND THENCE TO A FOURTH AND FINAL POSITION; SAID SHAFT ARRESTING THE FLEXING OF SAID INTERMEDIATE PORTION AND THE MOVEMENT OF SAID FREE END WHEN SAID SECOND ASSEMBLY REACHES SAID THIRD POSITION, AND SAID FREE END WINDING AROUND SAID SHAFT AS SAID SECOND ASSEMBLY MOVES FROM SAID THIRD TO SAID FOURTH POSITION TO EFFECT WIPING OF SAID SECOND CONTACT SURFACE ON SAID FLAT CONTACT SURFACE IN A DIRECTION OPPOSITE FROM SAID GIVEN DIRECTION. 